The subject of the invention is a device for breaking off the wire-like or strip-like electrode for an electro-erosion machine, wherein the electrode is supplied from the feed side and at the delivery side is deposited behind the workpiece which is to be processed.
Wire erosion machines, in particular those which are numerically controlled, can be used very advantageously for cutting complicated outer or inner contours on electrically conductive workpieces. As is known, during the processing operation wire-like or strip-like electrodes and workpieces move relative to one another. See U.S. Pat. No. 3,822,374 incorporated herein by reference. The electrode is drawn off from a feed roller, moves past the workpiece which is to be processed and passes through a drive device which consists of a pair of rollers which imparts a uniform feed motion to the electrode. Finally the electrode is rewound onto a roller and deposited. In the case of the known take-up roller, at the delivery side the electrode which is no longer to be used is wound up. This has the disadvantage that the roller must be changed when it is full. Moreover during the erosion process the electrode is subjected to such stress and deformation that loop formations and tangling can occur on the roller during the wind-up process.
It is already known to provide, at the delivery side, a cutting device which cuts the electrode into small pieces with the aid of a mechanical or magnetically moving blade and causes the pieces to fall into a collector container. See U.S. Pat. No. 3,822,374. However, this known cutting device does not operate reliably and therefore is unsuitable for automatic operation at night or on weekends. The cutting process cannot be carried out reliably since the electrodes, which consists of high-grade copper, produce deposits on the cutting tool and cause the workpiece to become smeared. In addition, the cutting tool is also subject to heavy wear. If the electrode is not cut off, hold-ups occur in the discharge of the electrode at the delivery side which lead to short-circuits and to the breakdown of the machine.